The present invention relates to a perpendicular magnetic recording and reproducing thin film head. More particularly, it relates to a thin film head of a structure which has a high recording density and high recording and reproducing efficiencies, which exhibits excellent magnetic characteristics and which is easy of fabrication.
Various structures have heretofore been proposed as magnetic recording and reproducing thin film heads, and the section of the principal portion of a typical example thereof is shown in FIG. 1. Referring to the figure, numeral 1 designates a nonmagnetic substrate, numeral 2 a lower magnetic layer, numeral 3 an inorganic insulator layer which effects the electrical insulation between the lower magnetic layer 2 and a conductor coil indicated by numeral 4, and numeral 5 an organic insulator layer which effects the electrical insulation between the conductor coil 4 and an upper magnetic layer formed of a magnetic film of high permeability indicated by numeral 6. It is required of a perpendicular magnetic recording head that one magnetic layer be rendered very thin into a main magnetic pole for executing recording and reproduction, while the other be rendered very thick into an auxiliary magnetic pole for forming a closed magnetic path (refer to, for example, Japanese Laid-open Patent Application No. 52-82318). It has heretofore been often the case that the lower magnetic layer is thickened into the auxiliary magnetic pole and that a substrate of a magnetic substance such as Mn-Zn ferrite functins as both the lower magnetic layer and the substrate (refer to, for example, Japanese Laid-open Utility Model Registration Application No. 57-75617). In this manner, in the conventional perpendicular magnetic recording thin film head, (1) the lower magnetic layer serves as the auxiliary magnetic pole for forming the closed magnetic path and is considerably thicker than the upper magnetic layer, and usually it is not patterned, (2) the upper magnetic layer serves as the main magnetic pole for executing recording and reproduction, and it is patterned into a proper shape in order to form recording and reproducing tracks, and (3) in general, in order to decrease the recording current of the conductor coil, the coil is wound spirally (the coil is called a " multi-turn coil"). With the thin film head of such a structure, it is difficult to attain good magnetic characteristics of the main magnetic pole. The reasons are that the upper magnetic layer forms a high step pattern (ordinarily, a step of approximately 10 .mu.m), so the magnetic characteristics are liable to degrade at the step part, and that on account of the multi-turning of the coil intended to enhance the current efficiency, an undulation (small ruggedness) corresponding to the coil pattern is liable to appear in the upper magnetic layer, so the magnetic characteristics degrade. Another disadvantage is that a high dimensional accuracy of the main magnetic pole is not realized in either of cases of patterning the high step by etching and forming the pattern by such a process as sputtering with a mask. Especially when the upper magnetic layer is thick, the patterning is, in effect, impossible. It is therefore difficult to thicken the other part than a part A (shown in FIG. 1) concerned in the recording and reproduction and facing to a magnetic recording medium, thereby to reduce the magnetic reluctance and to raise the efficiencies.
The following references are cited to show the state of the art; (i) Japanese Laid-open Patent Application No. 52-82318, and (ii) Japanese Laid-open Utility Model Registration Application No. 57-75617.